a gas-filled tube that has three electrodes and can be switched between an 'off' state and an 'on' state. It has been superseded, except for application involving high-power switching, by the thyristor
Word origin
C20: originally a trademark, from Greek thura door, valve + -tron
thyratron in American English
(ˈθaɪrəˌtrɑn)
US
noun
a hot-cathode, triode or tetrode, electron tube containing low-pressure gas or metal vapor in which one or more grids control the start of the current flow but have no further control over it